Having made peace and now living among the Vikings, the dragons' natural behavior leads to chaos on the Isle of Berk. This causes Stoick to reconsider allowing the dragons to roam freely on Berk. It is up to Hiccup and his friends to convince him otherwise.

The dragons unintentionally cripple Berk's food productivity by terrifying the local livestock, and with the year's first winter storm coming, the dragon-riding Viking youths of Berk must try and familiarize the local animals with their dragon companions if they are to have enough food for the winter.